General circuits for indirecting and distributing measurement in quantum computation

Abstract

A question of theoretical and practical interest is how a quantum system may be measured indirectly by means of an ancilla that interacts with it, and furthermore, how a system of ancillas may be used to implement a coherent measurement of spatially separated qudits. We provide general circuits that can be used to implement such measurements. These circuits are relevant to quantum error correction, measurement-based quantum computation and Bell state discrimination across a quantum network involving multiple parties. The last mentioned problem is treated in detail. Our circuitry can also help to optimize the quantum communication complexity for performing measurements in distributed quantum computing.